On 14/04/2025 21:41, Adrián Larumbe wrote:
> On 14.04.2025 11:01, Steven Price wrote:
>> On 11/04/2025 16:03, Adrián Larumbe wrote:
>>> Allow UM to label a BO for which it possesses a DRM handle.
>>>
>>> Signed-off-by: Adrián Larumbe <adrian.laru...@collabora.com>
>>> Reviewed-by: Liviu Dudau <liviu.du...@arm.com>
>>> Reviewed-by: Boris Brezillon <boris.brezil...@collabora.com>
>>
>> Reviewed-by: Steven Price <steven.pr...@arm.com>
>>
>> Although very minor NITs below which you can consider.
>>
>>> ---
>>> drivers/gpu/drm/panthor/panthor_drv.c | 42 ++++++++++++++++++++++++++-
>>> drivers/gpu/drm/panthor/panthor_gem.h | 2 ++
>>> include/uapi/drm/panthor_drm.h | 23 +++++++++++++++
>>> 3 files changed, 66 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c
>>> b/drivers/gpu/drm/panthor/panthor_drv.c
>>> index 06fe46e32073..983b24f1236c 100644
>>> --- a/drivers/gpu/drm/panthor/panthor_drv.c
>>> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
>>> @@ -1331,6 +1331,44 @@ static int panthor_ioctl_vm_get_state(struct
>>> drm_device *ddev, void *data,
>>> return 0;
>>> }
>>>
>>> +static int panthor_ioctl_bo_set_label(struct drm_device *ddev, void *data,
>>> + struct drm_file *file)
>>> +{
>>> + struct drm_panthor_bo_set_label *args = data;
>>> + struct drm_gem_object *obj;
>>> + const char *label;
>>> + int ret = 0;
>>> +
>>> + obj = drm_gem_object_lookup(file, args->handle);
>>> + if (!obj)
>>> + return -ENOENT;
>>> +
>>> + if (args->size && args->label) {
>>> + if (args->size > PANTHOR_BO_LABEL_MAXLEN) {
>>> + ret = -E2BIG;
>>> + goto err_label;
>>> + }
>>> +
>>> + label = strndup_user(u64_to_user_ptr(args->label), args->size);
>>> + if (IS_ERR(label)) {
>>> + ret = PTR_ERR(label);
>>> + goto err_label;
>>> + }
>>> + } else if (args->size && !args->label) {
>>> + ret = -EINVAL;
>>> + goto err_label;
>>> + } else {
>>> + label = NULL;
>>> + }
>>> +
>>> + panthor_gem_bo_set_label(obj, label);
>>> +
>>> +err_label:
>>> + drm_gem_object_put(obj);
>>> +
>>> + return ret;
>>> +}
>>> +
>>> static int
>>> panthor_open(struct drm_device *ddev, struct drm_file *file)
>>> {
>>> @@ -1400,6 +1438,7 @@ static const struct drm_ioctl_desc
>>> panthor_drm_driver_ioctls[] = {
>>> PANTHOR_IOCTL(TILER_HEAP_CREATE, tiler_heap_create, DRM_RENDER_ALLOW),
>>> PANTHOR_IOCTL(TILER_HEAP_DESTROY, tiler_heap_destroy, DRM_RENDER_ALLOW),
>>> PANTHOR_IOCTL(GROUP_SUBMIT, group_submit, DRM_RENDER_ALLOW),
>>> + PANTHOR_IOCTL(BO_SET_LABEL, bo_set_label, DRM_RENDER_ALLOW),
>>> };
>>>
>>> static int panthor_mmap(struct file *filp, struct vm_area_struct *vma)
>>> @@ -1509,6 +1548,7 @@ static void panthor_debugfs_init(struct drm_minor
>>> *minor)
>>> * - 1.2 - adds DEV_QUERY_GROUP_PRIORITIES_INFO query
>>> * - adds PANTHOR_GROUP_PRIORITY_REALTIME priority
>>> * - 1.3 - adds DRM_PANTHOR_GROUP_STATE_INNOCENT flag
>>> + * - 1.4 - adds DRM_IOCTL_PANTHOR_BO_SET_LABEL ioctl
>>> */
>>> static const struct drm_driver panthor_drm_driver = {
>>> .driver_features = DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ |
>>> @@ -1522,7 +1562,7 @@ static const struct drm_driver panthor_drm_driver = {
>>> .name = "panthor",
>>> .desc = "Panthor DRM driver",
>>> .major = 1,
>>> - .minor = 3,
>>> + .minor = 4,
>>>
>>> .gem_create_object = panthor_gem_create_object,
>>> .gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table,
>>> diff --git a/drivers/gpu/drm/panthor/panthor_gem.h
>>> b/drivers/gpu/drm/panthor/panthor_gem.h
>>> index af0d77338860..beba066b4974 100644
>>> --- a/drivers/gpu/drm/panthor/panthor_gem.h
>>> +++ b/drivers/gpu/drm/panthor/panthor_gem.h
>>> @@ -13,6 +13,8 @@
>>>
>>> struct panthor_vm;
>>>
>>> +#define PANTHOR_BO_LABEL_MAXLEN PAGE_SIZE
>>> +
>>> /**
>>> * struct panthor_gem_object - Driver specific GEM object.
>>> */
>>> diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
>>> index 97e2c4510e69..12b1994499a9 100644
>>> --- a/include/uapi/drm/panthor_drm.h
>>> +++ b/include/uapi/drm/panthor_drm.h
>>> @@ -127,6 +127,9 @@ enum drm_panthor_ioctl_id {
>>>
>>> /** @DRM_PANTHOR_TILER_HEAP_DESTROY: Destroy a tiler heap. */
>>> DRM_PANTHOR_TILER_HEAP_DESTROY,
>>> +
>>> + /** @DRM_PANTHOR_BO_SET_LABEL: Label a BO. */
>>> + DRM_PANTHOR_BO_SET_LABEL,
>>> };
>>>
>>> /**
>>> @@ -977,6 +980,24 @@ struct drm_panthor_tiler_heap_destroy {
>>> __u32 pad;
>>> };
>>>
>>> +/**
>>> + * struct drm_panthor_bo_set_label - Arguments passed to
>>> DRM_IOCTL_PANTHOR_BO_SET_LABEL
>>> + */
>>> +struct drm_panthor_bo_set_label {
>>> + /** @handle: Handle of the buffer object to label. */
>>> + __u32 handle;
>>> +
>>> + /**
>>> + * @size: Length of the label, including the NULL terminator.
>>> + *
>>> + * Cannot be greater than the OS page size.
>>> + */
>>> + __u32 size;
>>> +
>>> + /** @label: User pointer to a NULL-terminated string */
>>> + __u64 label;
>>> +};
>>
>> First very minor NIT:
>> * NULL is a pointer, i.e. (void*)0
>> * NUL is the ASCII code point '\0'.
>> So it's a NUL-terminated string.
>
> Fixed
>
>> Second NIT: We don't actually need 'size' - since the string is
>> NUL-terminated we can just strndup_user(__user_pointer__, PAGE_SIZE).
>> As things stand we validate that strlen(label) < size <= PAGE_SIZE -
>> which is a little odd (user space might as well just pass PAGE_SIZE
>> rather than calculate the actual length).
>
> The snag I see in this approach is that the only way to make sure
> strlen(label) + 1 <= PAGE_SIZE would be doing something like
>
> label = strndup_user(u64_to_user_ptr(args->label), args->size);
> if (strlen(label) + 1 <= PAGE_SIZE) {
> kfree(label)
> return -E2BIG;
> }
You can just do
strndup_user(u64_to_user_ptr(args->label), PAGE_SIZE)
If you look at the kernel's implementation it handles an overly long
string by returning an error:
> length = strnlen_user(s, n);
>
> if (!length)
> return ERR_PTR(-EFAULT);
>
> if (length > n)
> return ERR_PTR(-EINVAL);
>
> p = memdup_user(s, length);
So there's no need to call strlen() on the result.
> In the meantime, we've duplicated the string and traversed a whole page
> of bytes, all to be discarded at once.
>
> In this case, I think it's alright to expect some cooperation from UM
> in supplying the actual size, although I'm really not an expert in
> designing elegant uAPIs, so if you think this looks very odd I'd be
> glad to replace it with.
>
> Actually, as I was writing this, I realised that strndup_user() calls
> strnlen_user(), which is publicly available for other drivers, so
> I might check the length first, and if it falls within bounds, do
> the actual user stringdup.
Again, no need (and strnlen_user() has a comment basically saying "don't
call this"). strndup_user() has all the magic we need here.
As I say this is just a 'nit' - so no big deal. But I don't really see
the point of the size in the uAPI.
Take a look at dma_buf_set_name() for an example which sets the name on
a dma_buf (and doesn't take a size argument) - although that wasn't an
example of good uAPI design as the type in the ioctl was botched ;(
Thanks,
Steve
> I shall also mention the size bound on the uAPI for the 'label' pointer.
>
>> Thanks,
>> Steve
>>
>> +
>> /**
>> * DRM_IOCTL_PANTHOR() - Build a Panthor IOCTL number
>> * @__access: Access type. Must be R, W or RW.
>> @@ -1019,6 +1040,8 @@ enum {
>> DRM_IOCTL_PANTHOR(WR, TILER_HEAP_CREATE, tiler_heap_create),
>> DRM_IOCTL_PANTHOR_TILER_HEAP_DESTROY =
>> DRM_IOCTL_PANTHOR(WR, TILER_HEAP_DESTROY, tiler_heap_destroy),
>> + DRM_IOCTL_PANTHOR_BO_SET_LABEL =
>> + DRM_IOCTL_PANTHOR(WR, BO_SET_LABEL, bo_set_label),
>> };
>>
>> #if defined(__cplusplus)
>
>
> Adrian Larumbe
